In order to provide a background of the known prior art reference is first made to a silkscreen printer which is intended for applying to print material a first printed pattern consisting of a first colour as described with reference to FIGS. 3 and 4 of the U.S. Patent Specification No. 4,589,335, which is considered equivalent to the content of the Canadian Patent Specification No. 1 197 138.
In the case of this known silkscreen printer, the printing table is carried by a parallel linkage system by means of which the horizontal printing table is moved to a lower position for the movement of gripping means, and to an upper position in which printing of a pattern onto the printing material takes place.
During the time in which the gripping means displaces the print material from the material laying-on position to the printing position on the printing table, the printing table is located in its lower position and the gripping means pass over the printing table along stationary guide means.
However, when the gripping means are located above the printing table in a position for the application of print onto the print material, the printing table is raised to its upper position so that said print can be applied.
The print material is then deposited on the printing table by said gripping means and the printing table is lowered, whereafter the gripping means return to the earlier mentioned position and there collect further print material, at the same time as further gripping means grip the newly printed material, subsequent to raising the printing table.
It is also known in prior art silkscreen printer arrangements to arrange in the transport path of the print material a print material laying-on table, a silkscreen printer, a drying section, a depositing table, a further laying-on table, a further silkscreen printer, a further drying section and a further depositing table, etc., thereby to construct a single printing plant or "line" in which a multicolour print can be applied to a single piece of print material. It will be obvious that such a silkscreen printing line will occupy a large amount of space.
Thus, a silkscreen printer arrangement comprising a plurality of silkscreen printers and intended to apply a multicolour print onto one and the same piece of print material is known from the aforementioned U.S. Patent Specification No. 4,589,335.
The reason why a drying arrangement, which is normally highly space consuming, is required after each silkscreen printer is because the print applied to the print material in one silkscreen printer must be completely dry before further print is applied to the print material in the following silkscreen printer.
It is generally known that printing "wet-inwet" results in poor print quality when printing in silkscreen printers, since the undersurface of respective stencils is brought into contact with the wet print previously applied during a subsequent printing sequence.
Also known to the art are silkscreen printers which are constructed to apply a single colour pattern to print material, and that a plurality of such printers can be arranged in line for the purpose of obtaining a multicolour print.
One known silkscreen printer which can be used advantageously in the silkscreen printer arrangement according to the invention and which can be readily modified for multicolour print purposes is illustrated and described in the British Patent Specification No. 2 045 728.
It will also be noted that various types of drying apparatus are known to the art. One such drying apparatus which can be used advantageously in silkscreen printers, although subsequent to given modification, primarily to the printer, is one by means of which water based inks or pastes can be dried by means of electromagnetic waves at radio frequency. An example of one such drying apparatus is found illustrated and described in the U.S. Patent Specification No. 3,329,796.
It can also be mentioned that the U.S. Patent Specification No. 4,516,495 teaches, inter alia, a method of sensing the prevailing position of print material or print on the printing table, thereby enabling any discrepancies from a set-point value to be established, so that the position of a stencil frame can be adjusted towards this set-point value prior to transferring the stencil print onto the print material.